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Showing papers on "RNA-dependent RNA polymerase published in 1968"


Journal ArticleDOI
TL;DR: A method for measuring sequence homology between high specific activity RNA's and DNA of Xenopus laevis is described and the relative abundance of nucleotide sequences homologous to rRNA and 5 s RNA in X. laevIS liver, erythrocyte, and embryonic DNA has been found to be similar.

361 citations



Journal ArticleDOI
J. Borsa1, A.F. Graham1
TL;DR: Purified reovirus particles contain a polymerase which transcribes virus-specific mRNA in vitro from the double-stranded, viral RNA genome, and the enzyme activity is markedly increased after heat-shocking the virions.

165 citations


Journal ArticleDOI
TL;DR: The concept that 45S RNA is not a precursor of 5S RNA strongly supports the concept that neither the 45S component, nor any of the intermediates involved in its transition to 28S and 18S RNA, are involved in controlling the output of the 5S genes.
Abstract: To determine whether transcription of the genes coding for 5S ribosomal RNA depends upon the concurrent activity of the genes for 28S and 18S ribosomal RNA we studied the synthesis of 5S RNA in cultured L cells when the synthesis of the 45S precursor of 28 and 18S RNA was inhibited with low doses of actinomycin D. Synthesis of 5S RNA was measured by following the incorporation of 3H uridine into components which, upon acrylamide gel electrophoresis, co-migrated with markers of 5S RNA obtained from 32P labeled ribosomes. We observed that the synthesis of 5S RNA persists in the absence of detectable 28S and 18S RNA synthesis, continuing at the normal rate for several hours and at a reduced rate for at least a generation time. This strongly supports the concept that 45S RNA is not a precursor of 5S RNA, and indicates furthermore that neither the 45S component, nor any of the intermediates involved in its transition to 28S and 18S RNA, are involved in controlling the output of the 5S genes The 5S RNA which is made during actinomycin treatment is retained predominantly in the nucleoplasm and undergoes a turnover of about 3.5% per hour. It apparently cannot be utilized when ribosome synthesis resumes following removal of the actinomycin.

162 citations



Journal ArticleDOI
TL;DR: The RNA metabolism in immature duck erythrocytes has been investigated in order to determine the characteristics of messenger RNA (mRNA) in a highly differentiated animal cell.
Abstract: The RNA metabolism in immature duck erythrocytes has been investigated in order to determine the characteristics of messenger RNA (mRNA) in a highly differentiated animal cell. mRNA-like fractions were obtained from polysomes, on the one hand, and from pulse-labeled total cells or isolated nuclei, on the other, and were characterized by sedimentation, labeling kinetics, base composition, and hybridization to homologous DNA. At the translational level, the pulse-labeled RNA from polysomes consists of a predominant species sedimenting with about 9S and of a class of polydisperse material sedimenting between 6 and 28S. Very little ribosomal RNA (rRNA) is synthesized. The 9S RNA has been purified. Its base composition is relatively high in G + C (but different from rRNA or transfer RNA) – as determined, after alkaline hydrolysis, by 32P distribution or spectrophotometric analysis. The polydisperse RNA has a base composition characterized by relatively high proportions of U and A and is similar in this respect to nuclear RNA. Total polysomal RNA hybridizes to homologous DNA. The biological activity tested in a cell-free protein-synthesizing system of Escherichia coli is highest in the 16 to 18S zone of polysomal RNA. The rapidly labeled RNA synthesized at the transcriptional level in the nuclei sediments predominantly in the 30 to 80S zone. Base-composition analysis of this RNA reveals the presence of a predominant fraction of high-U-type RNA and of a small amount of 45 and 32S rRNA precursors. The former fraction — tentatively termed nascent, messenger-like RNA (nascent mlRNA), with respect to its base composition and capacity of selective hybridization — is metabolically more unstable than the precursor rRNA. Hybridization experiments demonstrate that up to 7% of the DNA is homologous to the nascent RNA fractions. Polysomal RNA hybridizes to a much smaller extent and competes only slightly with the heavy nuclear fractions. The significance of this heavy, nascent mlRNA and its eventual role in the regulation of protein synthesis in animal cells is discussed. We conclude that in a highly differentiated cell many more mRNA species are produced than would be expressed phenotypically through protein synthesis in the polysome. A surprisingly large part of the genome is activated, but an important fraction of the transcription products never reaches the sites of protein synthesis. Thus, the spectrum of functional RNA is not defined through synthesis only, but is restricted during metabolism. Under these conditions, control of differentiation is probably not limited exclusively to the transcription of the genome, but is subject to regulation mechanisms operating at the intermediate or translational level.

143 citations


Journal ArticleDOI
TL;DR: The SV40†-specific RNA in virus-yielding and in transformed cells has been characterized by DNA-RNA hybridization and by base ratio determinations on the hybridized RNA.

140 citations


Journal ArticleDOI

118 citations


Journal ArticleDOI
TL;DR: The three factors were found to be localized in a cell fraction in which ribosomes are associated with DNA, suggesting that in vivo they participate in the initiation of protein synthesis on messenger RNA before its release from the DNA template.

115 citations


Journal ArticleDOI
TL;DR: Inhibition of protein synthesis by addition of cycloheximide at the time of infection permitted only a limited number of the double-stranded viral RNA segments to be transcribed, suggesting that the early messengers might be synthesized by a pre-existing polymerase.

113 citations


Journal ArticleDOI
01 Jul 1968-Virology
TL;DR: Results indicate that guanidine does not inhibit growth and completion of viral RNA chains, but blocks the initiation of new chains in cells that are actively producing virus.

Journal ArticleDOI
TL;DR: It is postulate that the altered structure of the 45-S RNA does not permit this conversion of rRNA to tRNA, and synthesis of tRNA is not inhibited by toyocamycin, as shown by the ratio of methylation to nucleoside incorporation.

Journal ArticleDOI
19 Oct 1968-Nature
TL;DR: In this study, the objective was to demonstrate the ability of the H2O/H2O “spatially aggregating” substance to be converted into RNA by the enzyme DNA–RNA hybridization.
Abstract: IT is generally believed that genetic transcription is carried out by an enzyme, DNA-dependent RNA polymerase1, which is capable of copying DNA sequences into RNA sequences. The enzyme requires DNA and the four naturally occurring ribonucleotide triphosphates to produce RNA which is a faithful copy of the DNA template2 in terms of base composition, nearest neighbour analysis and DNA–RNA hybridization3.

Journal ArticleDOI
19 Oct 1968-Nature
TL;DR: The rifamycins and their semi-synthetic derivatives such as rifampicin inhibited the RNA polymerase of E. coli by inhibiting the initiation of RNA synthesis after theRNA polymerase has already combined with the DNA.
Abstract: THE rifamycins and their semi-synthetic derivatives such as rifampicin inhibited the RNA polymerase of E. coli1. Instead of interacting with the DNA, they appear to act on the RNA polymerase itself2, inhibiting the initiation of RNA synthesis after the RNA polymerase has already combined with the DNA3,4.

Journal ArticleDOI
26 Jan 1968-Science
TL;DR: Gliotoxin inhibits intracellular replication of poliovirus in HeLa cells at a stage subsequent to adsorption and penetration of virus.
Abstract: Gliotoxin inhibits intracellular replication of poliovirus in HeLa cells at a stage subsequent to adsorption and penetration of virus. The sensitive step is synthesis of viral RNA: synthesis of viral protein is unaffected except as a consequence of blockade of RNA synthesis. Concentrations of gliotoxin sufficient to block viral RNA synthesis completely do not affect cellular RNA synthesis.

Journal ArticleDOI
01 Aug 1968-Virology
TL;DR: The Harris strain of Sendai virus was compared with the L-Kansas strain of Newcastle disease virus with respect to viral RNA structure and virus-specific RNA synthesis in infected chick embryo fibroblast cultures to find that the RNA's from these two subgroup 2 myxoviruses are indistinguishable in sedimentation rate and overall base composition.

Journal ArticleDOI
TL;DR: The effect of spermidine and spermine on the synthesis of RNA in vitro by RNA-polymerase from Escherichia coli has been studied and models based on these results are proposed to explain the mechanisms of polyamine induced stimulation of RNA polymerase activity.
Abstract: The effect of spermidine and spermine on the synthesis of RNA in vitro by RNA-polymerase from Escherichia coli has been studied. Spermidine did not change the pH optimum of the reaction. With a high ratio of DNA to polymerase in the reaction mixture, maximal stimulation was observed at a spermidine concentration of 0.8 mM and spermine concentration of 0.3 mM. Under these conditions spermidine increased the initial velocity and the extent of the reaction. When the weight ratio of DNA to enzyme was low, the same concentration of spermidine increased the extent, but not the initial velocity of the reaction. If the reaction was primed by denatured DNA, spermidine did not stimulate the synthesis of RNA. A slight inhibition was observed at low concentrations of the template. Spermidine counteracted the inhibitory effect of RNA added to the reaction mixture before the start of the reaction. Models based on these results are proposed to explain the mechanisms of polyamine induced stimulation of RNA polymerase activity.

Journal ArticleDOI
TL;DR: The interaction of viral RNA with the smaller ribosomal subunit may be a necessary step in the formation of a functional polysome and the prevention of this interaction may explain the antiviral action of interferon.

Journal ArticleDOI
TL;DR: The effect of an antimicrobial antibiotic, streptovaricin, was studied on DNA-dependent RNA-synthetic reaction by RNA polymerase which was extracted from Ehrlich ascites carcinoma cells in a soluble state and showed no inhibition of the reaction.

Journal ArticleDOI
TL;DR: The absence of competition between ribosomal 18 S RNA and 28 S RNA for the DNA of isolated nucleoli and nuclei indicated that there were distinct sequences of DNA complementary to the two ribosome RNAs, and the base composition of preribosomal RNAs indicated that the conversion of nucleolar 45 S RNA to nucleolar28 S RNA was accompanied by a progressive increase in the content of adenine and a decrease in thecontent of uracil.

Journal ArticleDOI
TL;DR: It is possible that host cell DNA-dependent RNA polymerase is involved in the replication of influenza virus RNA.
Abstract: Deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase activity was assayed on nuclear preparations of chick embryo fibroblast cells at various times after infection with an influenza A virus (fowl plague virus) and was compared with the activity of uninfected cells. Polymerase activity was increased by about 60% by 2 hr after infection, and this increase coincided with an increase in RNA synthesis in infected cells, as determined by pulse-labeling with uridine. No difference could be detected between the polymerases of infected and uninfected cells as to their requirements for DNA primer, divalent cations, and nucleoside triphosphates, and they were equally sensitive to addition of actinomycin D to the reaction mixture. It is possible that host cell DNA-dependent RNA polymerase is involved in the replication of influenza virus RNA.

Journal ArticleDOI
TL;DR: Alkaline digestion of STNV ‡ 5′-[ 32 P]RNA prepared by such enzymic phosphorylation yielded stoichiometrically correct quantities of 5′- 32 pAp, thus establishing the5′-terminal nucleoside as adenosine.


Journal ArticleDOI
TL;DR: Chromatin isolated from control and 2,4-dichlorophenoxyacetic acid-treated soybean hypocotyl tissue incorporates labeled nucleoside triphosphates into acid-insoluble RNA into which RNA synthesis is inhibited by pyrophosphate and actinomycin D.

Journal ArticleDOI
02 Nov 1968-Nature
TL;DR: The results suggest that the role of factor is to promote a step in the reaction occurring after association of the enzyme with Qβ-RNA, but before nucleotide polymerization.
Abstract: THE Escherichia coli bacteriophage Qβ contains RNA as its genetic component. Qβ-RNA can be synthesized in vitro in the reaction catalysed by the Qβ-RNA polymerase isolated from Qβ infected E. coli1. The synthesis of infectious Qβ-RNA requires, in addition to the polymerase, the phage RNA to serve as template, ribonucleoside tri-phosphate substrates, Mg++, and a factor fraction obtained from both infected and uninfected E. coli2. Previous studies with the factor have suggested that it acts on Qβ-RNA at some early step in the reaction2. Although an association of the enzyme and Qβ-RNA occurs in the absence of this factor3, synthesis of the complementary minus strand is not detected. The requirement for this agent in the reaction seems to bear a quantitative relationship to Qβ-RNA but not to enzyme2. The factor fraction, furthermore, is not required for enzyme activity when synthetic polymers4, minus strands or other RNA molecules3 are used as template. These results suggest that the role of factor is to promote a step in the reaction occurring after association of the enzyme with Qβ-RNA, but before nucleotide polymerization.


Journal ArticleDOI
29 Jun 1968-Nature
TL;DR: RNA polymerase activity in isolated mitochondria of Saccharomyces cerevisiae precedes that of other respiratory enzymes, and may be of functional significance in mitochondriogenesis.
Abstract: RNA polymerase activity has been observed in isolated mitochondria of Saccharomyces cerevisiae. Increase in this activity precedes that of other respiratory enzymes, and may be of functional significance in mitochondriogenesis.



Journal ArticleDOI
TL;DR: It is concluded that significant amounts of E. coli RNA are synthesized during the first minutes of T4 infection, and this represents RNA synthesized by bacteria that had escaped infection.
Abstract: The ribonucleic acid (RNA) synthesized at specified intervals during infection of Escherichia coli K-12 by bacteriophage T4 was hybridized to denatured E. coli or T4 deoxyribonucleic acids (DNA). The reactions were performed under conditions that maximized the yield and at RNA/DNA inputs such that excess DNA sites were available for all RNA species. Most of the RNA synthesized at any time during the first 3 min of infection was host-specific. The fraction declined rapidly as infection progressed; host RNA represented about half that made between 3 and 4 min. It is unlikely that this represented RNA synthesized by bacteria that had escaped infection, as judged by the kinetics of adsorption and killing as well as by the rapid inhibition of beta-galactosidase induction after infection. The nature of the host RNA was also examined. Part of the RNA synthesized during infection of cells rendered sensitive to actinomycin was stable in the presence of this inhibitor. This RNA was essentially all host-specific and it sedimented as ribosomal and transfer RNA; most of the ribosomal RNA was incorporated into 30S and 50S ribosomes. Hybridization analyses suggested that unstable E. coli messenger RNA was also synthesized for several minutes after infection; the proportion of unstable to stable host RNA synthesized appeared to be similar in infected and uninfected cells. Thus, it is concluded that significant amounts of E. coli RNA are synthesized during the first minutes of T4 infection. Host messenger RNA initiated after infection may not be translated into enzymes; alternatively, it is conceivable that continued bacterial messenger RNA synthesis only reflects the completion of transcription of operons whose reading was initiated prior to infection.